Organometallic reactions, fine chemical synthesis

Catalytic liquid phase semihydrogenation of acetylenes is an important industrial and laboratory reaction, especially in fine chemical synthesis [1]. The use of supported metal catalysts for this selective hydrogenation readily facilitates the separation of organic products from the catalyst. However, liquid phase reactions with supported catalysts tend towards mass transport limitation [2] and, therefore, the support particles should be between 1 and 10 pm in size this avoids transport limitations and separation problems. With support particles of this size high temperature reduction in a flow of H2 gas is very difficult and to avoid this step it is possible to prepare supported metal particles by decomposing organometallic compounds under mild conditions [3-5]. 

The past four years have been characterized by more and more diverse applications of aqueous organometallic chemistry for the synthesis of fine chemicals. Useful classical transformations have been realized in aqueous solutions. The recycle of the transition metal catalyst has sometimes been possible, but the main importance at this early stage lies in the reactions themselves. 

The C-H transformation in the synthesis of fine chemicals can be separated in reactions employing catalysis by organometallic compounds and metal-free synthesis. Organometallic catalyzed functionalization is usually performed in liquid or gas/liquid reactions whereas the metal-free synthesis of fine chemicals often occurs as a gas-phase reaction. 

The most intensive development of the nanoparticle area concerns the synthesis of metal particles for applications in physics or in micro/nano-electronics generally. Besides the use of physical techniques such as atom evaporation, synthetic techniques based on salt reduction or compound precipitation (oxides, sulfides, selenides, etc.) have been developed, and associated, in general, to a kinetic control of the reaction using high temperatures, slow addition of reactants, or use of micelles as nanoreactors [15-20]. Organometallic compounds have also previously been used as material precursors in high temperature decomposition processes, for example in chemical vapor deposition [21]. Metal carbonyls have been widely used as precursors of metals either in the gas phase (OMCVD for the deposition of films or nanoparticles) or in solution for the synthesis after thermal treatment [22], UV irradiation or sonolysis [23,24] of fine powders or metal nanoparticles. 

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